Another use case for WaitProf – diagnosing “events in waitclass Other”

I recently diagnosed a performance issue where the “events in waitclass Other” occasionally took significant part of the session’s response time. For example Snapper (which reads wait event data from V$SESSION_EVENT) reported that during measuring 39.9% of the response time was spent on “events in waitclass Other”.

From Oracle 10g Oracle has consolidated lots of the events into “events in waitclass Other”. This is because saving all 900+ wait event stats for every session (in V$SESSION_EVENT array) would waste too much memory with giving little benefit (normally there’s only a handful of troublemaking events anyway). Therefore makes sense to aggregate the least likely happening events under some common category. Looks like Oracle kernel coders have set a threshold in event number above which all events are grouped under the “other” waitclass.